Conventional carpets are generally constructed by inserting a piling yarn through a primary backing fabric (also referred to herein as "primary carpet backing" or "primary backing", to form tufts of yarn which project from the surface of the fabric. The piling yarn may be inserted through the use of a tufting needle, which penetrates the primary carpet backing. The primary backing is then coated with an adhesive to secure the yarn to the primary backing, and to allow a secondary carpet backing (or "secondary backingy") to be affixed to the primary backing. A primary backing may be made of a woven fabric, or may be made of a non-woven fabric.
One type of conventional primary carpet backing may comprise a woven fabric, made of warp yarns and fill yarns. The term "fill yarn" may also be known as a "weft yarns" or "woof yarn." Woven carpet backings are easier to process through tufting than non-woven carpet backings and have the to "heal" from tufting penetrations. The term "heal" refers to the hole caused by a tufting needle closing once the needle is removed from the backing.
Woven carpet backings, however, suffer from a drawback i.e., a woven fabric backing can skew and bow as the warp and fill yarns shift position in relationship to each other. Skewing and bowing can show up as defects when patterns are tufted into a carpeting. Such defects may be especially apparent when long lengths of carpeting are required.
Another conventional primary carpet backing comprises a non-woven fabric. A non-woven fabric is usually defined as an assembly of textile fibers joined by mechanical interlocking in a random web or mat. Fibers may also be joined by fusing (in the case of thermoplastic fibers) or by bonding with a cementing medium, such as starch, glue, casein, rubber, latex, a cellulose derivative, or a synthetic resin. Non-woven fabrics generally have greater dimensional stability than woven fabrics, thereby lessening the chance of defects when patterns are used in a carpet. Non-woven carpet backings generally have weights of about 4 oz./yd..sup.2.
Non-woven fabric backings, however, suffer from a drawback, i.e., that the non-woven fabric does not heal after penetration of a tufting needle. The use of non-woven fabric backings may lead to increased tufting machine maintenance costs due to damage and friction on the tufting needle.
One type of a secondary carpet backing, designed to prevent bleed-through and sold by Shaw Industries, appears to be a composite material consisting of a woven fabric ("or woven component") mechanically coupled to a non-woven fabric (or "non-woven component"). The woven component consists of monofilament warp yarns, and spun fill yarns. These yarns are woven into a leno weave with a construction estimated at 16 ends per inch (warp yarns) and 5.5 picks per inch (fill yarn). The non-woven component can be a 3 oz./yd..sup.2 weight needle-punched fabric. The fiber used in the non-woven component appears to be polypropylene, with an estimated fiber denier range from 4 to 6 inches, and an estimated fiber length ranging from 21/2 to 3 inches in length.